Drug and alcohol use among America's teens continues to trend downward, according to new numbers released today by the Department of Health and Human Services. From 2002 to 2013, the average American teenager's odds of regular (at least monthly) tobacco use nearly halved. Recreational use of prescription painkillers saw a similar decline.

The rate of regular alcohol use among teens aged 12 to 17 declined from from 17.6 percent to 11.6 percent over the same period. Teen marijuana use, a contentious topic now that several states have legalized marijuana sales, is also on the decline.

These findings come from the 2013 National Survey on Drug Use and Health (NSDUH), an annual, nationally-representative survey of roughly 70,000 Americans aged 12 and older. Because of its large sample size the survey is considered an authoritative account of the nature and scope of drug, alcohol and tobacco use in the United States.

"We're seeing really exciting numbers in terms of the 12 to 17 year-olds across the country," according to Peter Delany, the director of the Center for Behavioral Health Statistics and Quality (CBHSQ) at the Substance Abuse and Mental Health Services Administration. "We see illicit drug use down significantly from 2009. We see marijuana starting to trend downward. Hallucinogens and inhalants are also down slightly."

"The 2013 NSDUH results suggest that the Administration’s efforts to reduce drug and alcohol use among young people is working," the White House Office of National Drug Control Policy (ONDCP) said in a press release.

Among all Americans, the survey finds that drug use trends are essentially flat. The percentage of those aged 12+ using any illicit drug in the past month is up slightly year-over-year, from 9.2 percent in 2012 to 9.4 percent in 2013. These numbers are driven primarily by a similar uptick in marijuana use over the same period.

The numbers suggest that ONDCP efforts to curb some of the most dangerous drug behavior, like opioid abuse, may be bearing fruit. "We’re especially heartened by the decrease in new initiates [that is, first-time use] of prescription drug misuse, which aligns with our prevention efforts," said ONDCP spokeswoman Cameron Hardesty.

The new figures on marijuana use come as several states are debating whether and how to legalize and regulate the marijuana market. Much of the discussion has centered around whether legalized marijuana would lead to increased adolescent marijuana use, which has been linked with poor health and education outcomes later in life.

Opponents of legalization often argue that it leads to a declining perception of risks associated with marijuana use among teens, which in turn leads to increased rates of adolescent use. But while the latest NSDUH data shows a continued drop in perceived risk of marijuana use among adolescents, overall teen use rates have actually trended slightly downward.

"One question that might be asked is how long the idea that adolescent cannabis use is driven by risk perception can survive the fact that risk perceptions have been falling, but prevalence hasn't been rising," said Mark Kleiman, a UCLA professor of public policy who studies drug policy.

Moreover, teens are also more likely to say that marijuana is difficult to obtain today than they were ten years ago. Taken together, these numbers suggest that evolving public attitudes toward marijuana use haven't made adolescents more likely to use the drug, nor have they made it easier to obtain.

Jonathan Caulkins, a Carnegie Mellon researcher who studies drug use, notes that there's a strong link between tobacco use and marijuana use, particularly among adolescents. Caulkins suspects that the sharp decline in teen tobacco use is keeping marijuana use levels low: "Success in anti-smoking [efforts] appears to have been 'protective' for youth," he said in an email. Peter Delany of the CBHSQ calls that "a plausible hypothesis." He notes a similar connection between teen alcohol use and illicit drug use, and says that efforts to curb tobacco and alcohol may be having "a spillover effect" on other drugs.

Among all Americans, the new numbers show that relaxed attitudes toward marijuana so far haven't translated to higher rates of dependence - 1.6 percent of Americans aged 12+ met the definition of marijuana dependency, essentially unchanged over the past decade. Alcohol dependency has crept downward over the same period.